Quite commonly waste products containing fluid-like materials such as garbage, fish water, cannery waste or the like are transported in mobile cargo containers over public roads and highways. The liquid nature of these waste products and the lack of fluid tight cargo boxes results in leakage from the cargo box onto the roads. Due to the slimy nature of many of these waste products, any leakage onto the highway is not only environmentally undesirable, but also may create slippery areas on the roadway which are hazardous to other vehicles. In order to prevent leakage therefrom, some cargo containers are made integrally formed sides and bottom wherein access to the inside of the container for loading and unloading is through the container top. Typically, it is desirable to provide for the discharge of waste-type cargo materials through the rear of the cargo box by providing a gate at the rear of the cargo box which is closed when the materials are being transported. In order to reduce the time and manpower necessary for unloading, a motorized conveyor endless chain, including laterally disposed flights, is located across a majority of a floor located above the bottom of the cargo box and upon which the cargo is deposited during loading. Discharge of the cargo material is accomplished by opening the cargo door and activating the conveyor endless chain which propels the lateral flights in a rearward direction to automatically discharge the materials along the floor and out the rear of the cargo box. Sometimes, cargo material such as cannery waste is discharged into a silage area of limited size which is enclosed by one or more walls. As the materials are discharged from the cargo box onto the floor of the silage area, and against one of the walls of the silage enclosure, a procedure is utilized wherein a buildup of discharged materials between the wall and the rear of the truck and conveyor causes the truck to be pushed in a forward direction (when brake is off and truck is in neutral gear), resulting in a tightly packed compact mass of deposited material in the silage area.
Conventionally, cargo containers have been constructed such that the rearward ends of the conveyor and container floor terminate coincident with the rearward edge of the container bottom. Some of the material which has a tendency to adhere to the conveyor during its vertical travel at the rearward end of the container will be deposited onto the bottom of the container during the conveyor's return trip to the front of the container. This incomplete discharge necessitates periodic cleaning of the container bottom to prevent buildup of this non-discharged material. In addition, this non-discharged material comes into contact with the conveyor sprocket and drive mechanism which can cause jamming of and damage to this equipment particularly when the cargo materials consist of tough fibrous material such as cornstalks and the like. The tendency of non-discharged material to be deposited below the floor onto the bottom of the cargo box is further aggravated when the conveyor is used to compact the discharged material in a silage area as described previously. In U.S. Pat. No. 4,199,292--Kasten, there is disclosed a forage wagon including an endless belt conveyor assembly for discharging forage material through a rear discharge opening; the forage wagon including a rear access door having a baffle assembly to enclose the conveyor rear drive assembly in order to prevent the forage material from entangling the conveyor rear drive assembly.
In order to provide for complete discharge of materials from the cargo box, conventional cargo containers include a conveyor assembly which extends rearwardly and beyond the container rear discharge opening and container bottom so that materials adhering to the conveyor fall to the ground and not onto the container floor. In U.S. Pat. No. 4,335,991--Sweetin, et al, there is disclosed a mobile cargo box including an endless drag chain for removing material from the cargo box through a rear discharge opening; the cargo box including a downwardly inclined segment which defined a rear discharge chute upon which the cargo materials were deposited allowing for gravitational discharge of the materials from the cargo box. Conventional cargo containers which utilize conveyor systems extending rearwardly and beyond the floor of the cargo box experience problems with leakage of fluid-like materials from the cargo box. Typically, a portion of the conveyor drive sprockets and conveyor belt extends through openings in the bottom of the cargo box or cargo door. Leakage of fluid-like materials from the cargo box through these openings is not uncommon. In U.S. Pat. No. 4,068,769--Sweet, et al, there is disclosed a cargo box including a conveyor assembly extending rearwardly beyond the end of the container floor, and a tank at the rearward end of the container floor for collecting liquid which percolate through the load. In U.S. Pat. No. 3,176,884--Klouda, there is disclosed a material container having a conveyor assembly and a flexible end gate which seals the rear end of the container to prevent the escape of fluidized materials, and wherein the flexible panel yields upon impaction by container flights passing over the rear edge of the container such that the seal is generally retained except for the momentary passage of the chain flights. Although conventional cargo boxes have reduced the problem of materials adhering to the conveyor by extending the conveyor rearward beyond the end of the container bottom, maintaining a fluid tight enclosure to prevent the escape of fluids from the cargo box has remained a problem.
There are numerous apparatus and methods for closing a container discharge outlet. In general, conventional means for sealing the discharge outlet of a railway hopper have utilized a sliding door in conjunction with a supported ledge member proximate to the end of the closing movement travel to support the leading edge of the sliding door in the closed position. In U.S. Pat. No. 3,106,899--Dorey, there is disclosed a hopper discharge outlet fitted with a sliding closure which upon sliding closing movement, the closure is inclined such that the leading edge of the closure rests upon the support ledge. In U.S. Pat. No. 4,006,692--Chierici, there is disclosed a railroad hopper outlet assembly including a sliding door wherein the forward edge of the sliding door engages support members in the closed position. In U.S. Pat. No. 3,485,183--Floehr, there is disclosed a railway hopper car outlet assembly including a sliding door wherein the leading edge is pressed in a downward direction against a hopper wall by one or more wedge members.
Other conventional apparatus and methods for closing a container include U.S. Pat. No. 4,263,863--Leitch, wherein there is disclosed a cover for a container which includes a recessed area for receiving a cover projecting member therein to guide the cover into a closed position.